Approved with cover card of the old disintegration and now switch

Hello, I have sold my old vehicle and registered my X5 with the cover card of my previous insurance. Now the insurance representative was there and calculates a contribution (UK, HP, TK) for my X5 with 2200.- Euro (SF25/17). At the HUK24 e.g. the car costs only 1200.- Euro. I have not signed the contract yet. Can I now conclude the contract with another insurance company although I have allowed with the cover card of my old insurance? eht, how do you do it then. Greetings herriup